The present invention relates generally to blast hole drills which have a mast and a rotary head mounted on a carriage for movement along the mast. More particularly, the present invention is directed to the manner in which the rotary head carriage is mounted for movement along the mast.
Blast hole drills are large earth drilling machines typically used in mining operations to drill holes for explosives. A conventional blast hole drill comprises a frame supported by crawlers for movement over the ground. A drill deck having a large rectangular opening is supported by the frame. A mast is supported by the frame for movement relative to the frame between a vertical position and a plurality of non-vertical positions. A drill pipe or drill string is supported relative to the mast, and a drill cutter bit is connected to a lower end of the drill pipe. The drill pipe extends through the opening of the drill deck and the shape of the opening allows the drill pipe to be positioned at the desired angle relative to the drill deck for drilling purposes. A rotary head engages an upper end of the drill pipe and moves along the mast. The rotary head rotates the drill pipe, and thus the drill cutter bit, into the ground.
The rotary head is mounted on a carriage which in turn is mounted on the cords forming the mast. The mast cords include a rack, and the rotary head includes a drive opinion which engages the rack in order to move the carriage up and down along the mast. The rotary head carriage is mounted on the mast by having the drive pinion and an idler pinion spaced from the drive opinion on one side of a mast cord, and a plurality of backup wheel assemblies on the opposite side of the cord opposite each of the pinions.
In prior constructions, the backup wheels were fixedly held in place against the mast cord. A mechanism, such as an adjustable mounting hole, was provided in order to adjust the position of the backup wheels relative to the mast. By varying the distance between the backup wheels and the mast cord, a clearance between the mast cord and the backup wheels was provided. This clearance was necessary to allow for differences in tolerances in the width of the mast cord as the rotary head moved along the mast. This spacing, however, permitted some movement of the rotary head carriage relative to the mast. This resulted in occasional vibration or xe2x80x9cchatterxe2x80x9d of the rotary head relative to the mast. This chatter produced undesirable noise and damage to the rotary head carriage and the mast.
One of the principal features of this invention is the provision of a mechanism for mounting the rotary head on the mast, with the rotary head being held against the mast with sufficient force so that no chatter can occur between the rotary head and the mast.
Another of the principal features of the invention is the provision of such a mechanism where some allowance for changes in width of the mast cords is provided for.
The invention provides a blast hole drill comprising a frame supported for movement over the ground, and a mast supported by the frame for movement relative to the frame between a vertical position and a plurality of non-vertical positions, the mast being formed of a plurality of mast cords, at least two of which are fixed in parallel relationship to each other. The drill further includes a carriage, a rack on at least one of the parallel mast cords, and a rotary head mounted on the carriage and adapted to engage a drill pipe, the rotary head including a drive pinion on the rack for moving the rotary head carriage along the mast.
The drill also includes means for mounting the carriage on the parallel mast cords, the mounting means comprising having the drive pinion on one side of at least one of the mast cords, and a backup wheel assembly on the opposite side of the respective mast cord opposite the pinion and including a wheel holding assembly support rotatably supporting a backup wheel. The backup wheel assembly also includes a yoke having an opening through the yoke, and a plunger received in the yoke opening. The wheel assembly support is slidably received on the plunger, and resilient means extends around the plunger and between the yoke and the wheel holding assembly support. The backup wheel assembly also further includes means for fixing the resilient means against the wheel assembly support so that the wheel is pressed against the mast cord by the resilient means.
More particularly, the rotary head also includes an idler pinion spaced from the drive pinion. The drive pinion and the idler pinion are on one side of each of the mast cords, and there are at least a pair of backup wheel assemblies on the opposite side of the respective mast cord, each of the wheel assemblies being opposite one of the pinions. Further, there are at least two plungers, each of which is received in one of the yoke openings.
Still more particularly, the means for fixing the resilient means against the wheel assembly support comprises the resilient means extending between an abutment on the plunger and the wheel holding assembly support, and means for moving and fixing the plunger toward the mast cord relative to the yoke so that the wheels are held against the mast cord by the resilient means.
Still more particularly, the means for moving and fixing the plunger toward the mast cord relative to the yoke comprises the plunger being threaded in the opening through the yoke.
Other features and advantages of the invention will become apparent to those skilled in the art upon review of the following detailed description, claims and drawings in which like numerals are used to designate like features.